1. Field of the Invention
The present invention relates to a vehicle headlamp housing a lamp unit within a lamp body for emitting beams forward with a predetermined luminous intensity distribution.
2. Description of the Related Art
Heretofore, there are a known vehicle headlamp housing a lamp unit within a lamp body. JP-B-6-36321 discloses an example of a fog lamp for laterally displacing a luminous intensity distribution by laterally pivoting the ti t movable reflective mirror of a lamp unit in conformity with a rudder angle. The application of the lamp unit to the vehicle headlamp makes it possible to enhance the visibility of a road surface ahead of a vehicle.
However, difficulty arises in carrying out beam emission with a sufficient quantity of light in the direction of a winding road surface on which a vehicle is traveling when only laterally pivoting a movable reflective mirror of the lamp unit. When the vehicle travels on the winding road having a small curvature radius, or makes a turn at an intersection, the movable reflective mirror will have to be largely turned left and right. It is therefore difficult to carry out beam emission with a luminous intensity distribution conforming to the travel conditions of the vehicle because the luminous intensity distribution is considerably deformed in cases where the movable reflective mirror is largely pivoted in the lateral direction.
The present invention provides a vehicle headlamp which houses a lamp unit in a lamp body for emitting beams forward with a predetermined luminous intensity distribution and is capable of emitting beams with the predetermined luminous intensity distribution, and at emission angles according to the travel conditions of a vehicle.
The invention is arranged so that a luminous intensity distribution can laterally be displaced by laterally pivoting the whole lamp unit. The luminous intensity distribution itself can be varied by moving the component element of the lamp unit.
More specifically, a vehicle headlamp having a lamp body for housing a lamp unit for emitting beams forward with a predetermined luminous intensity distribution comprises:
a luminous intensity variable control mechanism for varying the luminous intensity distribution by moving a component element of the lamp unit according to the travel conditions of a vehicle; and
a pivot control mechanism for laterally pivoting the lamp unit according to the travel conditions of the vehicle.
The xe2x80x98lamp unitxe2x80x99 is not limited to a specific configuration but may be a so-called parabolic lamp unit having a reflector formed with a rotary parabolic surface with, for example, a rotary parabolic surface or the like as a reference. Alternately, the lamp unit may be a so-called projector type lamp unit having a light source disposed in a manner substantially coaxial with an optical axis extending in the longitudinal direction of the vehicle, a reflector for reflecting light from the light source forward closer to the optical axis, a condenser lens provided in front of the reflector, and a shade which is provided between the condenser lens and the reflector and used for shielding part of the light reflected from the reflector.
In connection with the light source of the xe2x80x98lamp unitxe2x80x99, it is not limited to a specific one in construction but may be a discharge light-emitting portion of a discharge bulb, or the filament of an incandescent bulb such as a halogen bulb, or the like.
The xe2x80x98travel conditions of a vehiclexe2x80x99 means various conditional quantities regarding the travel of a vehicle and external information. For example, travel conditions of a vehicle may include vehicle speed, a rudder angle, vehicle posture, a vehicle-to-vehicle distance with respect to any preceding car, weather, navigation data, and the like.
The xe2x80x98component elementxe2x80x99 of the lamp unit is not limited to a specific configuration or component, but may be any component capable of being used to vary the luminous intensity distribution of the lamp unit by moving the component element. For example, a component element may be a shade, a light source bulb, a reflector, and the like.
As described by the construction of the vehicle headlamp according to the invention, the vehicle headlamp is so arranged as to vary the luminous intensity distribution by moving the component element of the lamp unit housed in the lamp body with the use of the luminous intensity variable control mechanism. In addition, the luminous intensity distribution is so arranged as to be laterally displaced by using the unit pivot control mechanism to laterally pivot the lamp unit, by properly combining beam emission control performed by the luminous intensity variable control mechanism and the unit pivot control mechanism. Therefore, the beam emission can be carried out at the emission angle with the luminous intensity distribution conforming to the travel conditions of the vehicle. The result is improved visibility of the road surface ahead of the vehicle.
With the arrangement above, the adoption of the projector type lamp unit as a lamp unit makes obtainable the following effect.
More specifically, as the vehicle headlamp according to the invention is so arranged as to move the component element of the lamp unit and to laterally pivot the lamp unit itself, a space for the purpose must be secured in the lamp body. Therefore, the adoption of the projector type lamp unit whose lamp unit itself can be made compact results in reducing its space. In connection with the projector type lamp unit, moreover, there are many kinds of component elements selectable as movable components for varying their luminous intensity distributions (e.g., a condenser lens is also selectable), and thus the luminous intensity variable control mechanism is adaptable for suitable use in the structure of the vehicle headlamp.
The use of the shade as the movable component element permits delicate variation of the luminous intensity distribution by moving the shade, whereby a luminous intensity distribution fit for the travel conditions of the vehicle is obtainable.